The most common known mutation of TTR is called Val-30-Met, causing nerve damage and electrical problems with the heart. Another common mutation in the United States is Thr-60-Ala which causes thickening of the heart muscle. While transthyretin-mediated amyloidosis (ATTR) occurs in families
of nearly every ethnicity, there is one TTR variant, Val-122-Ile, that appears to be common in the African-American population. It is estimated that 4% of African Americans carry this mutant gene, comprising upwards of 25% of African American patients with amyloidosis. This mutation may be an often unrecognized cause of cardiac disease in African Americans.
In addition to ATTR, there are other gene mutations for different proteins that lead to amyloidosis. Though very rare, some of these include: AFib (from fibrinogen A α-chain);
AApoAI (from apolipoprotein AI); ALys (from lysozyme); and AGel (from gelsolin).